1. Field of the Invention
The present invention generally relates to a paper feeding apparatus for use in an image forming apparatus including an office machine such as an inkjet printer, and more particularly, to a paper feeding apparatus which has a finger device portion that presses both corners of a leading end of a sheet of paper with a predetermined pressure in an image forming apparatus, thereby enabling a pickup device to accurately pick-up papers sheet-by-sheet and preventing an undesirable phenomenon, such as a paper jam or double-or multi-sheet feed, during a paper pickup process.
2. Description of the Related Art
FIG. 1 shows a general paper feeding apparatus 1 of an inkjet printer, which is provided with a frame 10, serving as a paper stack or a paper tray, obliquely mounted on a rear or upper side of the printer to receive a plurality of paper sheets thereon, a pickup portion 20 mounted on an upper side of the frame 10 to pickup and feed the paper sheets from the paper stack on the frame 10, and a paper setting unit 30 aligning the paper sheet on the frame 10 so as to prevent an undesirable movement of the paper sheets and guarantee feeding of the paper sheets sheet by sheet.
The frame 10 is provided with a knock-up plate 11 which is resiliently supported by a knock-up spring (not shown).
The pickup portion 20 includes a pickup roller 22 which is disposed on a shaft 21 connected with a gear train (not shown) that transmits a driving force from a motor (not shown).
The paper setting unit 30 includes a release lever 12 rotatably mounted on a side of the frame 10 to be moved in association with the knock-up plate 11, a finger portion 14 arranged on a lower portion of the release lever 12 to press on the paper sheet at a right corner of a leading end for an accurate separation of the paper sheets one by one, and a paper guide 25 movable leftward and rightward along the knock-up plate 11.
An operation of the conventional paper feeding apparatus 1 constructed as above will be described.
First, for easy stacking the papers on the knock-up plate 11 of the frame 10 that serves as the paper tray, the release lever 12 is clockwise rotated. As a result, the release lever 12 pushes the knock-up plate 11 downward by a first locking member (not shown) thereof and by a second locking member (not shown) thereof a makes the finger portion 14 to move away from the knock-plate 11 against a recovering force of a tension spring 19.
Next, the paper sheets are stacked on the knock-up plate 11 of the frame 10, and the paper guide 25 is adjusted. Then the release lever 12 is rotated counterclockwise.
As a result, when the knock-up plate 11 is released from a pressing force of the first locking member of the release lever 12, the knock-up plate 11 is raised by a recovering force of the knock-up spring to press the paper sheet with a predetermined pressure to be in contact with the pickup roller 22.
Also, when the finger portion 14 is released from a pressing force of the second locking member of the release lever 12, the finger portion 14 is counterclockwise rotated about a hinge axle 17a by the recovering force of the tension spring 19. Accordingly, a certain side of the paper sheets, i.e., a right corner of the paper sheets in this instance, is pressed by a claw (not shown) of the finger portion 14 being pressed towards the knock-up plate 11.
Then, with a rotation of the pickup roller 22, the paper sheet is released from the claw with a predetermined friction and fed into the printer.
Conventionally, since the finger portion 14 of the paper setting unit 30 is arranged only with respect to the right corner of the leading end of the paper sheets, the paper sheet is skewed with respect to a left side of the paper sheet that does not contact the finger portion 14 when the paper sheet is picked up by the pickup roller 22.
Due to the paper skew, an image is improperly printed on the paper sheet. Also, as the paper sheet skews, the paper sheet is easily caught in rollers such as a transport roller, resulting in a paper jam.
There is another drawback of having the finger portion 14 at only one side of the paper stack. That is, as the paper stack is kept in the frame 10 for a long time, due to a paper weight, a temperature and humidity, the paper stack gravitates toward the left side where there is no finger portion 14, resulting in an impairment in the paper feeding, such as the paper jam, multi-sheet feed, or the like.